The invention generally is related to monitoring the flow of fluids through a conduit, and more particularly, to detecting the presence of air in a liquid in the conduit.
In patient care facilities, the infusion of a parenteral solution into a patient is typically achieved by suspending an inverted bottle or fluid reservoir above the patient and interconnecting a fluid administration set between the reservoir and the patient. The administration set includes a conduit through which a parenteral solution flows. The free end of the tubing is connected to a cannula that is inserted into a blood vessel of the patient.
An infusion pumping mechanism may be used in conjunction with the fluid administration set to facilitate fluid infusion to the patient at a prescribed and regulated flow rate. The pumping mechanism may be engaged along an intermediate length of administration set tubing and actuated to pump the parenteral fluid through such tubing at the prescribed rate.
A peristaltic pump is one such type of infusion pumping mechanism that uses sequential occlusion of the administration set tubing to move the fluid through the tubing and to the patient. Linear type peristaltic pumps include a plurality of adjacent reciprocating pumping fingers, the fingers being sequentially urged against a length of fluid administration set tubing to occlude adjacent segments thereof in wave-like action forcing fluid through the tubing.
In fluid administration systems, it is important that introduction of air into a patient's blood vessel be avoided. Should an excessive quantity of air be introduced into a blood vessel, a condition known as air embolism may result whereby an air bubble may form in the blood vessel causing a blood flow obstruction. Consequently, it is desirable to include a monitoring device to monitor the fluid flowing in the administration set tubing so that an attendant may be notified if air above a certain quantity has been detected in the tubing. Once air has been detected, measures may be taken to prevent air from being introduced into a patient's blood vessel.
Devices for detecting the presence of air in a fluid conduit have been developed, such devices including in one case, an acoustic means to transmit a signal through the fluid conduit to an acoustic receiver that then transmits the received signal to a processor. The processor analyzes the received signal to determine whether air is present in the fluid conduit.
In one prior art air detection device, a U-shaped base forms a cavity between the branches of the U. A first transducer, an ultrasonic transmitter, is mounted on one branch of the U and a second transducer, an ultrasonic receiver, is mounted to the opposing branch of the U, each having an ultrasonic lens protruding into the cavity. In this device, the transmitter and receiver are semi-circularly convex and are spaced apart to receive a flexible fluid conduit between them and compress the side walls of the fluid conduit to obtain good contact. Good contact between the transducers and the object under test is essential to avoid any leakage of the transmitter signal through the air around the object rather than through the object. Such leakage would be considered to be the detection of air by the processor and a false alarm may result. Thus, if a substantial surface area of each of the respective transducers is exposed to outside air, the signal-to-noise ratio will decrease and may result in false or inaccurate readings. Therefore, to minimize such signal-to-noise interference and improve signal strength, it is desirable to improve the surface contact area between the transducer and the surface of the fluid conduit, while in turn preventing the introduction of contaminants between them.
Another prior art device has a hollow U-shaped body, the respective branches of the U each mounting a concave ultrasonic transducer aligned in diametrically opposed positions, the transducers configured for receipt of a length of fluid conduit. When the fluid conduit is installed between the concave transducers, a length of fluid conduit is manually inwardly compressed by the user and manipulated between the concave transducers and the end of the U-shaped body. A concave cover is closed over the fluid conduit to slightly compress and encircle the conduit. Although this device has proven effective in use, it has been found desirous to have such a device constructed so that when the conduit is installed, such conduit is correctly aligned between the pair of transducers automatically without any undue effort.
Hence, those skilled in the art have recognized the need for a monitoring device for detecting the presence of air in a fluid conduit that provides a fluid conduit capturing feature for automatically aligning the fluid conduit adjacent sensing transducers. Furthermore, such device should provide improved surface contact between the transducer and the fluid conduit for increased monitoring accuracy. In addition, a device of this nature should be cost effective and easy to manufacture. The present invention fulfills these needs.